A case of renal cell carcinoma with microscopic pulmonary tumor embolism proven by surgical lung biopsy.

Pulmonary tumor embolism (PTE) is difficult to diagnose before death. We report the case of a 75-year-old man with microscopic PTE of renal cell carcinoma who was diagnosed by surgical lung biopsy. He visited our hospital because of dyspnea on exertion. Chest computed tomography (CT) showed multiple micronodules and ground glass opacities. Steroid therapy was started as therapeutic diagnosis for IgG4-related pulmonary disease. However, he was admitted our hospital due to progressive respiratory failure. Pathological findings of a lung biopsy obtained by video-assisted thoracic surgery showed PTE of renal cell carcinoma without embolization of large pulmonary arteries. He received palliative medicine and died four months after the surgical lung biopsy. In cases of multiple micronodules in chest CT findings and worsened respiratory symptoms, PTE should be considered in the differential diagnosis.